The present invention relates to a method for determining a coding type and a coding mode for object shape coding of an object-oriented video compressing technique in video compressing techniques which take aim at multimedia services of very low bit rate transmission such as video telephone and video conference services through a public switched telephone network and a mobile radio communication network. More particularly, the present invention relates to a method for determining a coding type and a coding mode for object shape coding which compresses an image by determining the coding mode based on the characteristic of an object and shape and varying a coding method according to the determined coding mode.
Generally, H.261 for providing video telephone and video conference services using an integrated services digital network (ISDN), and H.263 for providing the video phone service using a public switched telephone network (PSTN) have internationally been standardized. However, since H.261 and H.263 supplying a moving picture of a very low bit rate such as a video telephone have poor picture quality, the necessity of improving picture quality has been increased. As techniques related to the moving picture, there have been proposed MPEG1 (moving picture expert group 1) for DSM (digital storage media), and MPEG2 for DSM, HDTV (high definition television), ATV (advanced television), etc. However, H.261, H.263, MPEG1 and MPEG2 techniques adopt a coding method based on a block and thus the picture quality remarkably deteriorates in application to the very low bit rate transmission. To overcome this disadvantage, MPEG4 takes an access of a new method different from a conventional coding method, and various coding methods such as subband coding, region based coding, model based coding, object oriented coding, etc. are being considered.
In conventional shape coding using polygon and spline, instead of classifying circumstances according to the characteristic of an object or similarity between object shape, only a case having a small error value is selected by calculating an error of the shape between a motion-compensated predictive image of the previous image and the original image. Consequently, since a coding mode corresponding appropriately to circumstances is not set, unnecessary processing processes occur and coding gain deteriorates.